Spark plug



.LPETRUS SPARK PLUG Filed Aug. 30, 1920 March 24, 1925.

m m m m Patented Mar. 24, 1925.

UNITED STATES JOHN PET-BUS, 01' IILWAUKEE, WISCONSIN.

SPARK PLUG.

Application am August so, me. Serial in. 400,779.

To all whom it may concern: Be it known that I, Jomr Pmos, a citizen of the United States, residin at Milwaukee, county of Milwaukee, an State of 6 lVisconsin, have invented new and useful Improvements in Spark Plugs, of which the following is a specification.

This invention relates to spark plugs. Objects of this invention are to provide a spark plu which will automatically maintain a gas-tight joint between the insulating core and the metal casing; which has a nonfriable insulating core; which has an electrode so associated with the body portion that it will heat a separated portion of the charge prior to ignition; which has the body ortion arranged to separate a pure explosive mixture from the oil impregnated mixture and conduct such mixture to the electrode: 2 and which has a body portion so arranged that upon firing a tongue of flame isprojected with high velocity into the compressed charge in the cylinder.

Other objects of this invention are to provide a spark plug of simplified design which may be manufactured at a reduced cost and still secure the objects enumerated above.

An embodiment of the invention is shown in the accompanying drawings, in which-- Fig. 1 is a longitudinal sectional view ofthe plug.

Fig. 2 is a bottom plan view partly in section illustrating the interior construction of the plug.

The spark plug has a main body portion 1 threaded at 2 adjacent its lower end and arranged to screw into a cylinder. The upper portion may have a hexagonal contour 3 adapted to be engaged by a wrench in inserting the plug in a cylinder. This body portion 1 has a main inner cylindrical compartment 4 formed therein and has an outwardly extending duct 5 in communication therewith formed by a tubular portion 6 extending outwardly from the bottom web 7 of the bodv rtion 1. The upper inner portion ofthe body portion 1 is threaded as indicated at 7' so as to be engaged by the threaded gland 8 which also may be provided, if desired, with a hexagonal or knurled upper portion 9. This gland has a tapered central orifice in which is mounted the insulating member 10, also of conical contour. This insulating member is preferr ably formed of asbestos cement compound and thereby produces a non-friable insulator which will withstand high temperatures and pressures. A spindle 11 extends longitudinally thru this insulating member and is provided at its upper end with a washer 12, locking nut 13, and thumb screw 14 so as to be adapted for connection with the high tension leads of the ignition circuit. The lower portion of this spindle carries an enlarged disk-shaped electrode 15 having rounded upper and lower surfaces and a hub or shank portion 16 adapted to seat against the bottom portion of the insulating member 10, such electrode being pinned or otherwise secured to the spindle 11.

The electrode 15 is proportioned and positioned within the cylindrical cavity 4 so as to have the shortest distance between itself and the surrounding metal at its outer periphery. That is to say, when a spark forms, the arc will strike from the extreme outer edge of this electrode to the cylindrical walls of the cavity 4.

By actual experiment, it is found that the explosive mixture which passes upwardly thru the duct 5 into the cavity 4 upon compression, is not impregnated with lubricatmg oil as is the explosive mixture in the main body of the cylinder. It is found that practically pure explosive charges pass into the cavity 4 and that the oil is caught and retained along the outer side wall to the tube 6 in the cavity 16, thereby preventing clogging or fouling of the spark plug.

' By forming the electrode 15 of material size considerable heat is stored therein by the SUCCBSSlXB explosions and considerable surface is presented to the gas surrounding such electrode and enclosed within the cavity 4. Therefore, this enclosed gas is preheated before ignition occurs, thereby insuring a complete ignition and a relatively violent explosion in such cavity.

By providing the duct 5 extending outwardly from the cavity and of materially less diameter a great velocity of discharge is groduced thereby projecting the tongue of ame a great distance into the compressed explosive charge in the cylinder and producing a practically instantaneous, complete ex losion in the main cylinder.

t will be seen that the tube 6 directs the flaming gas outwardly from the cavity within the plug, and projects a tongue of flame 111W the gas withm the cylinder. Thu

tongue of flame is not broken up and diffused, but passes in a stream into the engine cylinderthereby reaching gas remote from the plug as well as gas adjacent thereto.

Altho the electrode 15 is described and shown as solid, it nevertheless may be hollow and may be provided with perforations as disclosed in my co-pending application, Serial No. 365347, filed March 13, 1920, for spark plugs.

It will thus be seen that a spark plug has been provided in which the gas-tight joint is automatically maintained and in which an adequate thermal and electrical insulation of the heated electrode is secured by the non-friable asbestos cement insulating member 10. It will also be seen that an electrode has been provided in which relatively pure combustible mixture is separated out from the main charge and preheated before ignition occurs and thereafter projected into the main charge with a violent motion so as to get a complete ignition of the entire compressed charge in the main cylinder.

I claim:

1. spark plug comprising'a main body portion of generally cylindrical construction having an inner cavity and an outer cavity, a web separating said cavities, a tube extending outwardlyfrom said web, from the inner cavity into the outer cavity, and a relatively large electrode positioned within said inner cavityand thermally insulated from other portions of said spark plug.

2. A spark plug comprising a main body portion of cylindrical formation, a web separating said body portion into inner and outer compartments, a tube extending outwardly from said web and-communicating with the inner compartment, a gland adapted to close said inner compartment, and an electrode positioned Wholly within said inner compartment and insulated from said gland.

In testimony whereof I affix my signature in the presence of two witnesses.

JOHN PETRUS. Witnesses:

LEVERETT C. WHEELER,

0. C. WEBER. 

